Reflex klystron having a two-potential reflector electrode



June 13, 1967 T. M. JACKSON 3,325,670

REFLEX KLYSTRON HAVING A TWO-POTENTIAL REFLECTOR ELECTRODE Filed July 9, 1963 Inventor THOMAS IV, JACKSON By %&

Attorney United States Patent 3,325,670 REFLEX KLYSTRON HAVING A TWO-POTENTIAL REFLECTOR ELECTRODE Thomas M. Jackson, London, England, assignor to International Standard Electric Corporation, New York, N.Y., a corporation of Delaware Filed July 9, 1963, Ser. No. 293,643 Claims priority, application Great Britain, July 19, 1962, 27,779/ 62 2 Claims. (Cl. 315-5.19)

This invention relates to reflex klystrons and is especially concerned with the construction and arrangement of a two potential reflector electrode in a reflex klystron.

In a reflex klystron oscillator a beam of electrons is projected through a cavity resonator and is reflected after passing through the interaction gap a first time to return bunched electrons for a second transit through the gap. In this process the repelling field must fulfill two functions. The equipotential field configuration must be suitable for refocussing the beam through the resonator aperture and the transit angle must be accurately defined to obtain correct phasing of the electron bunches for delivery of power to the resonator. There is no adequate theory that can be applied to reflector design and experimental design is complicated by a number of variable parameters, but may be simplified by the use of a multipotential reflector system.

It is therefore an object of the present invention to provide a simplified reflex klystron of improved efliciency, having a two-potential reflector electrode, the reflector electrode including a first outer tubular electrode and a second electrode insulated from the first electrode and mounted within and on the axis of the first electrode.

Although not limited to such use the invention is particularly applicable to millimeter Wave tubes in which alignment accuracy requirements are critical and the minute dimensions introduce difficulties in obtaining a practical design.

An embodiment of the invention will be described with reference to the accompanying drawing, which shows, partly in section, the reflector end of a millimeter wave reflex klystron according to the invention.

In the embodiment illustrated the body of the klystron is a cylindrical copper block 1 in which are formed two accurately profiled axial bores 2 and 3 approaching one another from opposite ends of the block and each separated by a metallic septum 4 and 5, respectively, from a cavity resonator 6, initially 'formed as part of one of the bores and completed by insertion of a closure plug forming an end wall of the resonator. A tapered wave-guide 7 formed in the block 1 is provided for extracting energy from the resonator 6. Each septum 4 and is centrally apertured for passage of an electron beam through the resonator. An electron gun 8, having a cathode 9 inside a focussing electrode 10, is fitted into the bore 3 opposite the resonator interaction gap, the septum 5 forming the anode of the gun.

An electron reflector electrode 11 is mounted on the opposite side of the resonator 6 within the bore 2. The reflector electrode 11 comprises a first outer tubular electrode 12 and a second rod-shaped electrode 13 axially within and insulated from the first electrode 12. The outer tubular reflector electrode 12 is formedwith a seating 14 and a screw-threaded end portion 15 by means of which it is secured, with the aid of a nut 16, in a ceramic bush 17. The bore 2 is shaped to provide a seating for the bush 17 and, nearer its open end, is widened out to receive an annular clamping member 18, which seats on the bush 17 and is held pressing against the upper surface of the bush by means of screws 19, of which one is shown.

The second, inner, reflector electrode 13 is a molybice denum Wire 20 which is coated, except for its ends, wit] an insulating glaze such as a suitable glass coating, so a to be a sliding fit Within the first outer electrode 12. Th inner electrode 13 is supported at its end remote from th cavity resonator 6 by an arm 21, secured to the wire 2t by means not shown, and supported on a column 22 mounted on the ceramic bush 17.

The open end of the bore 2 is closed by a copper plat 23, provided with a pair of terminals 24 for connection t1 the two potential reflector electrode 11. At its end th bore 2 is provided with a narrow internal seating 25 to the end of the closure plate 23, a pressure weld bein; formed around the seating 25 between it and the membe 23. A connection to the outer electrode 12 is provide by means of a tag 26, held under the nut 16, a lead being taken from the tag to one of the terminals 24. Connectior to the other electrode 13 is provided by a lead connecting the upper end 20 of this electrode with the other termi nal24.

If desired the support 22 may be made so as to perm-i adjustment before the end plate 23 is sealed into tht block; of the position of the resonator end of the elec trode 13 with respect to the end of the outer electrode 12 In the use of the invention it has been observed tha adjustment of the potentials applied to the two reflecto1 electrodes has marked effect on the output obtained. Ir some cases it was found that certain oscillating mode: were not obtainable with a common potential reflector Typical voltages to give optimum power output are shown in the table below. In this the potential of the outer reflector is measured with respect to the cathode oi the klystron and the inner reflector voltage is measurec' with respect to that of the outer reflector.

It is to be understood that the foregoing description of specific examples of this invention is not to be considered as a limitation on its scope as set forth in the appended claims.

I claim:

1. A reflex klystron including a cavity resonator formed in a cylindrical block of metal having aligned axial bores in each end and a respective septum of metal separating each bore from the cavity resonator, each septum being centrally apertured for passage of an electron beam through the resonator, a cathode assembly mounted in one bore to supply said electron beam and a two-potential reflector electrode being mounted in the other bore spaced from said cavity and respective septum, said reflector including a first outer tubular electrode and a second cylindrical electrode insulated from the first electrode and mounted within and on the axis of said first electrode, and means applying separate potentials to said first and second electrodes to return electrons through said aperture.

2. A reflex klystron as claimed in claim 1, wherein the second electrode is a glass-coated metal rod having an extending uncoated end.

(References on following page) 3 4 References Cited OTHER REFERENCES UNITED STATES PATENTS Jackson, Brisbane and Ashz High-Power Reflex Klysglarmoltz '5 313 i59 trons for Millimetre Wavelengths; Electrical Communicaang 5 5'2 5 tion, vol. 39, No. 3, 1964 (pp. 403-412).

' FOREIGN PATENTS Great Britain. Examiner. 728,932 4/ 1955 Great Britain. R. D. COHN, Assistant Examiner.

777,054 6/1957 Great Britain. 

1. A REFLEX KLYSTRON INCLUDING A CAVITY RESONATOR FORMED IN A CYLINDRICAL BLOCK OF METAL HAVING ALIGNED AXIAL BORES IN EACH END AND A RESPECTIVE SEPTUM OF METAL SEPARATING EACH BORE FROM THE CAVITY RESONATOR, EACH SEPTUM BEING CENTRALLY APERTURED FOR PASSAGE OF AN ELECTRON BEAM THROUGH THE RESONATOR, A CATHODE ASSEMBLY MOUNTED IN ONE BORE TO SUPPLY SAID ELECTRON BEAM AND A TWO-POTENTIAL REFLECTOR ELECTRODE BEING MOUNTED IN THE OUTER BORE SPACED FROM SAID CAVITY AND RESPECTIVE SEPTUM, SAID REFLECTOR INCLUDING A FIRST OUTER TUBULAR ELECTRODE AND A SECOND CYLINDRICAL ELECTRODE INSULATED FROM THE FIRST ELECTRODE AND MOUNTED WITHIN AND ON THE AXIS OF SAID FIRST ELECTRODE, AND MEANS APPLYING SEPARATE POTENTIALS TO SAID FIRST AND SECOND ELECTRODES TO RETURN ELECTRONS THROUGH SAID APERTURE. 